1. Field of the Invention
The present invention relates to a robot that includes a robot arm including a first frame and a second frame that are coupled to each other so as to be turnable about a joint axis, and a cable fixed to the robot arm while being laid along a side surface of the robot arm.
2. Description of the Related Art
In a joint portion of an industrial robot, a cable such as a power line, a signal line, and air piping is provided. Along with the rotation of the joint portion, the cable receives bending and twisting forces to be deformed. At this time, the cable may sag to repeatedly collide with and slide on a peripheral device, and thus the cable may be damaged. In particular, when the cable is air piping, the cable may bend at a small curvature radius to fluctuate the air pressure, or air may leak outside from a flaw generated in the cable.
In the joint portion of the industrial robot, the cable is generally wired so that the cable can twist along with the rotation of the joint portion. However, in order to enable cable twisting, it is necessary to provide the cable three-dimensionally in a rotational axis direction, which leads to a problem in that the joint structure is upsized. In view of this, some industrial robots have a configuration in which the cable is laid along the outer side of the joint portion so that the cable may be bent to follow the rotation of the joint portion.
Further, there has been proposed a device in which, at both ends of the joint portion, that is, on the side surfaces of the first and second frames, the cable is supported by brackets each formed of a plate spring, to thereby enable displacement and inclination of the fixing position (see Japanese Patent Application Laid-Open No. H10-34588). This configuration prevents the cable from being damaged due to excessive tension of the cable, and prevents contact to a peripheral device due to flexure.
However, in Japanese Patent Application Laid-Open No. H10-34588, the brackets are elastically deformed, and hence the cable moving along with the rotation of the joint portion may not be fixed by the brackets, and the entire cable may move along with the elastic deformation of the brackets. When the entire cable moves as described above, a force may act on a connection portion such as a connector, resulting in disconnection of the cable at the connection portion.
Therefore, the cable needs to be fixed on the side surface of each frame. However, when the cable is laid along the side surface of each frame, the cable may be bent by the bending movement about the joint axis, which may cause flexure of the cable in the joint axis direction. When the cable flexes in the joint axis direction as described above, the cable may repeatedly collide with or slide on a peripheral device.
To address this problem, there is a measure of placing the robot at a location distanced from the peripheral device to prevent contact of the cable to the peripheral device, but there is a problem in that the placement space is increased. Further, the cable may be repeatedly brought into contact with the robot arm itself, and hence the damage on the cable cannot be prevented only by placing the robot at a location distanced from the peripheral device.
Therefore, the following measure is conceivable to prevent cable damage. The cable may be covered with an exterior cover such as Cableveyor (trademark) or bellows so that the cable is prevented from being brought into direct contact with the robot arm and the peripheral device.
However, more space is required to mount the exterior cover, and hence there is a problem in that the robot is upsized. Further, when the cable flexes inside the exterior cover, the cable is repeatedly brought into contact with the inner wall of the exterior cover, and hence the damage on the cable cannot be effectively prevented.